If you right-click on entries for these applications from the left side of your Start Menu (when showing the list), you can choose to "Unpin from Start". Try that, and then "Pin to Start" again.
Tried that and although the tileicons did reappear, it was only temporary.
However, I was trying out some of the settings - Notifications etc and lo and behold, the Tile icons did reappear and so far (over a full day) they have remained. I am not sure which of the settings that I changed caused the sudden unexpected result as I didn't notice that the tile icons had reappeared right away.
As of right now, I *think* I have the icon issue fixed - time will tell.
Thanks all for the helpful replies.